BACKGROUND OF THE INVENTION
[0001] Embodiments of the invention relate generally to rotary machines and, more particularly,
to the reducing mixing of packing leakage and the main flow of hot gas or steam in
gas and steam turbines, respectively.
[0002] As is known in the art, turbines employ rows of buckets on the wheels / disks of
a rotor assembly, which alternate with rows of stationary vanes on a stator or nozzle
assembly. These alternating rows extend axially along the rotor and stator and allow
combustion gasses or steam to turn the rotor as the combustion gasses or steam flow
therethrough.
[0003] Axial / radial openings at the interface between rotating buckets and stationary
nozzles can allow hot combustion gasses or steam to exit the main flow and radially
enter the intervening wheelspace between bucket rows. In gas turbines, cooling air
or "purge air" is often introduced into the wheelspace between bucket rows. This purge
air serves to cool components and spaces within the wheelspaces and other regions
radially inward from the buckets as well as providing a counter flow of cooling air
to further restrict incursion of hot gasses into the wheelspace. Nevertheless, incursion
of combustion gasses or steam into the wheelspaces between bucket rows contributes
to decreased turbine efficiency of between about 1% and about 1.5%.
[0004] Document
JP 2004-100578 A discloses a blade part structure of an axial flow turbine. A moving rotor blade extends
from a platform which has a front edge. On the corner of the front edge of the platform,
there is positioned midway between adjacent rotor blades a guide groove. The guide
groove is provided to smooth horseshoe vortices and avoid leakage of hot working fluid
flow through a cavity between platforms of the rotor blades and of the stationary
blades, respectively.
[0005] Document
US 2014/0205443 A1 discloses a gas turbine engine including a stationary vane assembly and a rotary
blade assembly. A blade extends from a platform which has an axially upstream end
portion defining a seal assembly together with an axially downstream portion of the
vane assembly. The seal assembly comprises a regular pattern of plural blade grooves,
which in one embodiment are formed by opposing and generally straight sidewalls. Cool
purge gas may thereby pass out of the grooves and flow in the same direction as the
hot working gas while preventing ingestion of the working gas into a cavity between
the vane and blade assemblies.
[0006] Document
EP 2 581 555 A1 discloses a turbomachine component having a flow contour feature. The feature is
positioned on a front face of a base portion of a stage bucket from which an airfoil
portion extends. The feature takes the form of a non-axisymmetric trench or depression
and thereby alters local pressures at circumferential locations within a turbine portion
wheelspace in order to increase local backflow margins which prevents localized hot
gas ingestions from entering the wheelspace.
BRIEF DESCRIPTION OF THE INVENTION
[0007] The invention relates to the subject matter set forth in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] These and other features of this invention will be more readily understood from the
following detailed description of the various aspects of the invention taken in conjunction
with the accompanying drawings that depict various embodiments of the invention, in
which:
FIG. 1 shows a schematic cross-sectional view of a portion of a known gas turbine;
FIG. 2 shows a perspective view of the gas turbine of FIG. 1;
FIG. 3 shows a perspective view of a pair of turbine buckets according to an embodiment
of the invention;
FIG. 4 shows a radially-inward looking schematic view of turbine buckets according
to an embodiment of the invention;
FIG. 5 shows the turbine buckets of FIG. 4 in relation to hot gas flow; and
FIG. 6 shows a schematic view of a steam turbine bucket according to en embodiment
of the invention.
[0009] It is noted that the drawings of the invention are not to scale. The drawings are
intended to depict only typical aspects of the invention, and therefore should not
be considered as limiting the scope of the invention. In the drawings, like numbering
represents like elements among the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0010] Turning now to the drawings, FIG. 1 shows a schematic cross-sectional view of a portion
of a gas turbine 10 including a bucket 40 disposed between a first stage nozzle 20
and a second stage nozzle 22. Bucket 40 extends radially outward from an axially extending
rotor (not shown), as will be recognized by one skilled in the art. Bucket 40 comprises
a substantially planar platform 42, an airfoil extending radially outward from platform
42, and a shank portion 60 extending radially inward from platform 42.
[0011] Shank portion 60 includes a pair of angel wing seals 70, 72 extending axially outward
toward first stage nozzle 20 and an angel wing seal 74 extending axially outward toward
second stage nozzle 22. It should be understood that differing numbers and arrangements
of angel wing seals are possible and within the scope of the invention.
[0012] The number and arrangement of angel wing seals described herein are provided merely
for purposes of illustration.
[0013] As can be seen in FIG. 1, nozzle surface 30 and discourager member 32 extend axially
from first stage nozzle 20 and are disposed radially outward from angel wing seals
70 and 72, respectively. As such, nozzle surface 30 overlaps but does not contact
angel wing seal 70 and discourager member 32 overlaps but does not contact angel wing
seal 72. A similar arrangement is shown with respect to discourager member 32 of second
stage nozzle 22 and angel wing seal 74. In the arrangement shown in FIG. 1, during
operation of the turbine, a quantity of purge air may be disposed between, for example,
nozzle surface 30, angel wing seal 70, and platform lip 44, thereby restricting both
escape of purge air into hot gas flowpath 28 and incursion of hot gasses from hot
gas flowpath 28 into wheelspace 26.
[0014] While FIG. 1 shows bucket 40 disposed between first stage nozzle 20 and second stage
nozzle 22, such that bucket 40 represents a first stage bucket, this is merely for
purposes of illustration and explanation. The principles and embodiments of the invention
described herein may be applied to a bucket of any stage in the turbine with the expectation
of achieving similar results.
[0015] FIG. 2 shows a perspective view of a portion of bucket 40. As can be seen, airfoil
50 includes a leading edge 52 and a trailing edge 54. Shank portion 60 includes a
face 62 nearer leading edge 52 than trailing edge 54, disposed between angel wing
70 and platform lip 44.
[0016] FIG. 3 shows a perspective view of a pair of buckets 140, 240 according to an embodiment
useful for appreciating the invention. Here, bucket 140 includes a pair of recesses
192, 194 along platform 142 adjacent leading edge 152 of airfoil 150. Specifically,
platform 142 includes an upstream recess 192 and a downstream recess 194. Platform
242 includes a downstream recess 294 along platform 242 adjacent leading edge 252
of airfoil 250 and upstream recess 192 of bucket 140.
[0017] Recesses 192, 194, 294 may be machined into platforms 142, 242 according to any known
or later-developed method. Alternatively, recesses 192, 194, 294 may be cast as part
of platforms 142, 242.
[0018] FIG. 4 shows a radially-inward looking schematic view of three buckets 140, 240,
340 according to an embodiment of the invention. As in FIG. 3, upstream recess 192,
extends from leading edge 146 to upstream edge 145 of platform 142. Upstream recess
192 is adjacent downstream recess 294, which extends from leading edge 246 to downstream
edge 247 of platform 242. Similarly, upstream recess 292 extends from leading edge
246 to upstream edge 245 of platform 242. Upstream recess 292 is adjacent downstream
recess 394, which extends from leading edge 346 to downstream edge 347 of platform
342.
[0019] FIG. 5 shows a radially-inward looking schematic view of buckets 140, 240, 340 with
respect to the flow of hot gas 280, 380. Recesses 192, 294, 292, 394 alter the flow
of hot gas 280, 380. Specifically, recesses 192, 294, 292, 394 act to alter a swirl
of hot gas 280, 380, which is directed around a leading face 253, 353 of airfoils
250, 350, respectively. Directing hot gas 280 around leading face 253 of airfoil 250
reduces incursion of hot gas 280 between platforms 142 and 242 and into wheelspace
26 (FIG. 1). The reduction in incursion of hot gas 280 into wheelspace 26 improves
turbine efficiency. Typically, turbine efficiency is improved by up to about 0.08%
where recesses according to embodiments of the invention are employed in high-pressure
and/or intermediate-pressure stages of a gas turbine.
[0020] The extent to which the swirl of hot gas 280, 380 is altered depends, for example,
on the depth to which recesses 192, 294, 292, 394 extend radially inward into platforms
142, 242, 342. Typically, recesses 192, 294, 292, 394 extend radially inward into
platforms 142, 242, 342 to a depth up to about 2,54 mm (100 mil,i.e., about 0.1 inch),
e.g., to a depth between about 0,254 mm (10 mil) and about 2,54 mm (100 mil), or between
about 0,508 mm (20 mil) and about 2,29 mm (90 mil), or between about 0,762 mm (30
mil) and about 2,03 mm (80 mil), or between about 1,02 mm (40 mil) and about 1,78
mm (70 mil), or between about 1,27 mm (50 mil) and about 1,52 mm (60 mil).
[0021] Similarly, the extent to which the swirl of hot gas 280, 380 is altered depends on
the angles at which recesses 192, 294, 292, 394 are disposed relative to platform
leading edges 146, 246, 346. Downstream recesses 194, 294, 394 are typically angled
between about 45° and about 80° relative to platform leading edges 146, 246, 346.
Upstream recesses 192, 292, 392 are typically angled between about 90° and about 120°
relative to platform leading edges 146, 246, 346. As described herein and as shown
in FIGS. 3-5, the angles of recesses 192, 294, 292, 394 are angled as measured from
leading edge 146, 246, 346.
[0022] The principle of operation of the platform recesses described above with respect
to the operation of gas turbines may is also applicable to the operation of steam
turbines. For example, FIG. 6 shows a schematic side view of a steam turbine bucket
440 according to an embodiment of the invention. Magnified views A and B show radially-inward
looking views of platform 442 adjacent, respectively, upstream edge 445 and downstream
edge 447. In magnified view A, upstream recess 492 is shown angled at angle α relative
to leading edge 446. In magnified view B, downstream recess 494 is shown angled at
angle β relative to leading edge 446.
[0023] As noted above with respect to FIGS. 3-5, upstream recess 492 and downstream recess
494 extend radially inward into platform 442 to a depth up to about 2,54 mm (100 mil),
e.g., to a depth between about 0,254 mm (10 mil) and about 2,54 mm (100 mil), or between
about 0,508 mm (20 mil) and about 2,29 mm (90 mil), or between about 0,762 mm (30
mil) and about 2,03 mm (80 mil), or between about 1,02 mm (40 mil) and about 1,78
mm (70 mil), or between about 1,27 mm (50 mil) and about 1,52 mm (60 mil). Increases
in the efficiencies of steam turbines employing platform recesses according to embodiments
of the invention are similar to those described above with respect to gas turbines.
Typically, increases in efficiency of up to about 0.08% are observed.
[0024] As used herein, the singular forms "a," "an," and "the" are intended to include the
plural forms as well, unless the context clearly indicates otherwise. It will be further
understood that the terms "comprises" and/or "comprising," when used in this specification,
specify the presence of stated features, integers, steps, operations, elements, and/or
components, but do not preclude the presence or addition of one or more other features,
integers, steps, operations, elements, components, and/or groups thereof.
[0025] This written description uses examples to disclose the invention, including the best
mode, and also to enable any person skilled in the art to practice the invention,
including making and using any devices or systems and performing any related or incorporated
methods. The patentable scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other examples are intended
to be within the scope of the claims if they have structural elements that do not
differ from the literal language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal language of the claims.
1. A turbine bucket (140) comprising:
a platform (142) portion;
an airfoil (150) extending radially outward from the platform (142) portion; wherein
the airfoil (150) comprises a leading edge (152), a suction side and a pressure side,
the platform (142) portion comprising a leading edge (146) of the platform (142) portion
disposed adjacent the leading edge (152) of the airfoil, an upstream edge (145) disposed
adjacent the pressure side of the airfoil, and a downstream edge (147) adjacent the
suction side of the airfoil,
wherein at least one recess (192, 194) extends radially inward into the platform (142)
portion at the leading edge (146) of the platform portion,
characterized in that the at least one recess includes:
a downstream recess (194) extending from the leading edge (146) to a downstream edge
(147) of the platform (142) portion and angled at an angle (α) between 45 ° and 80°
relative to the platform leading edge (146) in a tangential plane on the platform,
and
an upstream recess (192) extending from the leading edge (146) of the platform (142)
portion to the upstream edge (145) of the platform (142) portion and angled at an
angle (β) between 90° and 120° relative to the platform leading edge (146) in a tangential
plane on the platform,
wherein further the at least one recess (192) extends radially inward into the platform
(142) portion to a depth up to 2,54 mm (100 mil).
2. The turbine bucket of any preceding claim, wherein, in an operative state, the at
least one recess (194) is adapted to change a swirl of hot gas (280) passing across
the platform (142) portion.
1. Gasturbinenschaufel (140), umfassend:
einen Plattform (142)-Abschnitt;
ein Schaufelblatt (150), das sich von dem Plattform (142)-Abschnitt radial nach außen
erstreckt; wobei
das Schaufelblatt (150) eine Vorderkante (152), eine Saugseite und eine Druckseite
umfasst,
der Plattform (142)-Abschnitt umfassend eine Vorderkante (146) des Plattform (142)-Abschnitts,
welches benachbart zur Vorderkante (152) des Schaufelblattes angeordnet ist, eine
anströmseitige Kante (145), welche benachbart zur Druckseite des Schaufelblattes angeordnet
ist, und eine abströmseitige Kante (147), benachbart zur Saugseite des Schaufelblattes,
wobei sich mindestens eine Aussparung (192, 194) radial nach innen in den Plattform
(142)-Abschnitt an der Vorderkante (146) des Plattformabschnitts erstreckt,
dadurch gekennzeichnet, dass die mindestens eine Aussparung folgendes einschließt:
eine abströmseitige Aussparung (194), die sich von der Vorderkante (146) zu einer
abströmseitigen Kante (147) des Plattform (142)-Abschnitts erstreckt und in einem
Winkel (α) zwischen 45° und 80° bezogen auf die Plattform-Vorderkante (146) in einer
Tangentialebene auf der Plattform abgewinkelt ist, und
eine anströmseitige Aussparung (192), die sich von der Vorderkante (146) des Plattform
(142)-Abschnitts zu einer anströmseitigen Kante (145) des Plattform (142)-Abschnitts
erstreckt und in einem Winkel (β) zwischen 90° und 120° bezogen auf die Plattform-Vorderkante
(146) in einer Tangentialebene auf der Plattform abgewinkelt ist,
wobei sich ferner die mindestens eine Aussparung (192) radial nach innen in den Plattform
(142)-Abschnitt bis zu einer Tiefe von bis zu 2,54 mm (100 mil) erstreckt.
2. Gasturbinenschaufel nach einem der vorstehenden Ansprüche, wobei, in einem Betriebszustand,
die mindestens eine Aussparung (194) angepasst ist, um einen Drall von Heissgas (280),
der den Plattform (142)-Abschnitt durchquert, zu ändern.
1. Aube de turbine (140) comprenant :
une partie de plate-forme (142) ;
une surface portante (150) s'étendant radialement vers l'extérieur à partir de la
partie de plate-forme (142) ; dans laquelle
la surface portante (150) comprend un bord d'attaque (152), un côté d'aspiration et
un côté de pression,
la partie de plate-forme (142) comprenant un bord d'attaque (146) de la partie de
plate-forme (142) disposée adjacente au bord d'attaque (152) de la surface portante,
un bord amont (145) disposé adjacent au côté de pression de la surface portante et
un bord aval (147) adjacent au côté d'aspiration de la surface portante,
dans laquelle au moins un évidement (192, 194) s'étend radialement vers l'intérieur
dans la partie de plate-forme (142) au niveau du bord d'attaque (146) de la partie
de plate-forme,
caractérisée en ce que l'au moins un évidement comprend :
un évidement aval (194) s'étendant du bord d'attaque (146) à un bord aval (147) de
la partie de plate-forme (142) et incliné selon un angle (α) entre 45° et 80° par
rapport au bord d'attaque de plate-forme (146) dans un plan tangentiel sur la plate-forme,
et
un évidement amont (192) s'étendant depuis le bord d'attaque (146) de la partie de
plate-forme (142) jusqu'au bord amont (145) de la partie de plate-forme (142) et incliné
selon un angle (β) entre 90° et 120° par rapport au bord d'attaque de plate-forme
(146) dans un plan tangentiel sur la plate-forme,
dans laquelle en outre l'au moins un évidement (192) s'étend radialement vers l'intérieur
dans la partie de plate-forme (142) jusqu'à une profondeur allant jusqu'à 2,54 mm
(100 mil).
2. Aube de turbine selon l'une quelconque des revendications précédentes, dans laquelle,
dans un état opérationnel, l'au moins un évidement (194) est adapté pour changer un
tourbillon de gaz chaud (280) passant à travers la partie de plate-forme (142).